2 Answers
2

are you sure? Back in the days when people keep on adding friends for facebook games, I thought there was a limit as somebody reached it.
–
SoarerSep 5 '11 at 4:15

@Soarer, I'm 99.9% sure, but as mark4o mentioned facebook has to have some kind of spam filters and if you request a 100 friends within a day and most of them refuse you you might be blocked for adding more.
–
GregSep 5 '11 at 17:04

It is not a fixed daily limit, however to prevent spam and abuse, Facebook may delay some friend request notifications or temporarily block you from sending more friend requests if you already have a number of unanswered friend requests, or if you send friend requests that are marked as spam, or the person says that they don't know you, or people report you, etc. Facebook does not disclose the details since that would give spammers an advantage. And it is likely that the details change over time as Facebook adapts to new spam and scams. It may also vary depending on whether you have verified your account (using a mobile phone, credit card, etc.).

A commonly suggested maximum is 20 friend requests per day, but some people have reported being blocked by Facebook for sending fewer than that and others have successfully sent more.

If you add friends too quickly this warning may pop up:

Warning! You are engaging in behavior that may be considered annoying or abusive by other users.

Facebook's systems determined that you were going too fast when adding friends. You must significantly slow down. Further misuse of site features may result in a temporary block or your account being permanently disabled. For further information, please visit our FAQ page.

If you see this you may want to stop sending friend requests for a couple days, or at least until several of your outstanding friend requests are accepted. You may also want to cancel outstanding friend requests that seem unlikely to be accepted. Although it is not clear which strategies actually work.

If you are temporarily blocked from sending friend requests you may see this:

Block! You are engaging in behavior that may be considered annoying or abusive by other users.

You have been blocked from adding friends because you repeatedly misused this feature. This block will last anywhere from a few hours to a few days. When you are allowed to reuse this feature, please proceed with caution. Further misuse may result in your account being permanently disabled. For further information, please visit our FAQ page.

or:

Block! You are engaging in behavior that may be considered annoying or abusive by other users.

Facebook's systems determined your friend requests are being rejected at a high rate. Facebook aspires to be an environment where people can interact safely with friends and people they know. Facebook has limits to prevent unsolicited friend requests because this behavior has been reported as annoying or abusive by other users.

Facebook has limits in place to prevent behavior that others may find annoying or abusive. These limits restrict the rate at which you can use certain features on the site. If you received a warning for going too fast when adding friends, you will need to temporarily stop this activity to avoid hitting a block on your account. To read more about our policies please click here.

Facebook has security systems to stop abusive actions. The systems automatically identify the following types of behavior:

Feature overuse: There are limits to restrict the rate at
which you can use features on the site. Overusing features is not
allowed because it may make other people feel annoyed or unsafe.

Unwanted contact: Our systems detect when friend requests
you send to others are being ignored at a high rate and volume. Using
Facebook to contact many people you don't know is not allowed because
it may make them feel threatened, harassed, or unsafe.

Further misuse of site features may result in a temporary block, or your account being permanently disabled from Facebook.